1. Field of the Invention
The present invention relates to an underframe of a body for a rolling stock and a method of manufacturing the same and, more particularly, to a method and an underframe construction for a rolling stock having equipment disposed beneath the underframe.
2. Description of the Prior Art
In, for example, "Rolling Stock Technology 159", A Japanese Association of Rolling Stock Industry, 29, (Sept., 1982) an underframe construction is proposed wherein, as shown in FIGS. 14-17, a body of a rolling stock comprises side frame means 1 for forming opposite side walls, a roof frame means 2 for forming a roof, an underframe means 3 for forming a floor or support, and end frame means 4 for forming longitudinal end walls.
As shown most clearly in FIG. 15, the underframe 3 includes longitudinally extending side sills 5 disposed on opposite sides of the underframe 3, end sills 9 connecting the corresponding opposite ends of the side sills 5, body bolsters 8 respectively placed at positions corresponding to trucks of the rolling stock, center sills 10 extending between the body bolsters 8 and the corresponding end sills 9, cross beams 6 extending between the side sills 5 and parallel to the body bolsters 8 at equal intervals, and a corrugated plate 7 placed on the upper surface of the
Another underframe construction has been proposed which includes extruded shapes of a hollow truss construction formed of an aluminum alloy arranged across the underframe and joined to the side sills.
Moreover, U.S. Pat. No. 4,645,258 proposes an underframe comprising side sills, and members having a box-shaped cross section placed contiguously in parallel to the side sills.
In the underframe illustrated in FIG. 16, the vertical size of the cross beams 6 must be large to bear vertical load and, consequently, the vertical size of the underframe is increased. Accordingly, the height of the passenger cabin must be reduced or a space for accommodating necessary equipment beneath the underframe must be reduced. Since the cross beams 6 must have a sufficient strength, the cross beams 6 are formed of a channel or comparatively thick plate in a -shaped cross section as shown in FIG. 17 and, consequently, the cross beams 6 are comparatively heavy.
On the other hand, the material cost of the underframe comprising extruded shapes formed of an aluminum alloy is high as compared with that of the steel underframe. Furthermore, since new extruded shapes must be prepared every time the specifications of the underframe are changed, additional costs are incurred for preparing new dies. Furthermore, an underframe consisting mainly of members formed of an aluminum alloy is susceptible to heat, and hence the underframe must be provided with heat insulating members to improve fire resistance.
Moreover, in an underframe comprising members having a box-shaped cross section contiguously placed longitudinally between the side sills, a longitudinal load, namely, a tractive force, is transmitted by the side sills, and hence the side sills must be sufficiently strong. Accordingly, such an underframe comprises heavy side sills, which increases the weight of the underframe.